Barrier beaches on Cape Cod prone to nature’s whims

Thursday

Jun 21, 2007 at 12:01 AMJun 21, 2007 at 9:15 PM

History does repeat itself, especially on the Outer Cape. One hundred and sixty one years ago a storm punched a hole through Chatham’s barrier beach, the part of Nauset Beach known as North Beach, in virtually the same spot as the new breach, created during the April nor’easter.

By Rich Eldred

History does repeat itself, especially on the Outer Cape.

One hundred and sixty one years ago a storm punched a hole through Chatham’s barrier beach, the part of Nauset Beach known as North Beach, in virtually the same spot as the new breach, created during the April nor’easter.

That’s the basic barrier beach story, as explained by coastal geologist Graham Giese at a recent forum sponsored by the Pleasant Bay Alliance in Chatham. And while one can’t make exact predictions on what will happen, based on history the general trajectory is the same.

“The south side of the (new) inlet will continue to erode and in that case shoals would develop coming in from the north island into the shore which result in the closing off of the present bay and the break would eventually go south to Watch Hill again,” Giese guessed.

After the break in 1846, the new channel migrated south, while the newly created island broke in half. Eventually the southern tip of Nauset beach migrated south of Chatham Light and as the beach got thinner it broke again in the 1987 storm, creating the current harbor outlet. The new breach is just part of that repeated pattern.

Looking at old maps it appears Minister’s Point and the mainland opposite the 1846 break suffered little, if any erosion, despite a large opening to the ocean.

John Ramsey, a coastal engineer with Applied Coastal Research and Engineering, pointed out that the locals even built a road right along the coastline around 1900.

“If you look at the navigation charts of 1885,” Ramsey said. “After (the barrier beach) started falling apart and moving landward it formed a large series of bars, Ram Island flats, that actually protected the shoreline from ocean waves.”

There is pretty heavy shoaling in the Minister’s Point area already.

“Aids to navigation are in place,” said Chatham’s Director of Coastal Resources Ted Keon. “But Minister’s Point is a mess.”

Keon is concerned the shoaling will clog access the fish pier.

“I’m really concerned about the navigation issue,” he said. “In ‘87 we had lots of shoaling. As the sand comes in there are very dire implications of trying to maintain access to the new inlet.”

The new inlet is actually the old inlet opposite the lighthouse. There are a number of reasons Keon believes filling the new breach with dredge spoils could be a good idea.

“The loss of camps on North Beach. They are in extreme danger. I anticipate virtually all of these camps will be lost. I can see the break widening. These camps don’t have much of a future,” he said. “We’ll probably lose camps on the south side also as it erodes.”

There is the threat of shoreline erosion, which claimed nine homes after the 1987 break, widespread armoring of the shoreline, perhaps the eventual closing off of the current harbor outlet, the loss of resources such as mussel and eelgrass beds and beachfront and public access due to armoring.

But the new breach has its positive side.

“Habitat quality all comes down to increasing tidal exchange as the water moves in and out,” explained Brian Howes of the Massachusetts Estuaries Project. “The more you have water going out that results in lower nitrogen levels and amelioration of degradation of the system due to nitrogen loads. So we would move from a tidal inlet that is less efficient to one that is more efficient.”

That of course, also happened in 1987. The tidal range increase as one moves north on Cape Cod.

“It is 5 to 6 feet opposite Ministers point vs. 3 to 4 near the current inlet,” Howes said.

“That results in better flushing of the bay. That increase has a positive impact on the ecological features of the bay.”

The break opposite Chatham Light in 1987 markedly improved flushing. The water quality, especially in Pleasant Bay’s upper reaches such as Meetinghouse Pond, improved by close to 40 percent.

“If we wanted to improve the system in 1985 we’d have asked why not cut a break a little further north and improve the inlet,” Howes reflected. “From the habitat point of view, from '86 to '87 it was a substantial improvement.”

The new breach won’t have quite that dramatic effect.

“We might be looking at a 10 percent to 15 percent improvement from where we are today,” Howes suggested. “We could lose eelgrass beds where the sand rolls over them but the habitat improvement will lead to colonies in other areas because of improved conditions,” Howes said.

Filling in the breach would not create a stable target either, as Giese predicted it would break through again.

“But looked at from the positive side filling will buy time for the interest potentially harmed by it, the fishing industry especially,” he said. “I don’t know how long it would be before it (would) break through again. I expect to have 10 to 20 years.”

The fact is barrier beaches are inherently unstable.

“The barrier beach is eroding rapidly at a rate of 6 feet a year or 1 mile over 1,000 years. The whole system is moving west,” Giese noted.

Much of the land, or what used to be land, involved in the breach belongs to the Cape Cod National Seashore.

“Where you put the sand is the issue because it’s the National Seashore. That’s the elephant in this room,” Keon said.

The elephant spoke near the forum’s end. Carrie Phillips, the chief resource officer of the Seashore was in attendance.

“Our policies are very clear and strong,” she said. “Our mission is to protect natural processes in a natural system. That said, if the town decides they want to look at intervention, it is our obligation to consider the negative impact of leaving the breach. The town, fishing fleet, homeowners are all involved in the analysis.”